Texture Studies of Superplastically Deformed Electrodeposited Nanocrystalline Ni and Ni-P Alloy

Abstract

Nanocrystalline Ni and Ni-P alloy with grain size down to 6 nm were processed by pulsed electrodeposition. The as-deposited materials, possessing a strong fiber texture, were tested in tension at different temperatures and strain rates. Both materials exhibited low temperature superplasticity but with significant differences in mechanical characteristics. In comparison with nano-Ni, the nano Ni-P alloy exhibited significant strain hardening in flow behavior and lower superplastic elongations at relatively low strain rates, although the grain size was finer at test temperatures with limited grain growth in nano Ni-P alloy. Texture study as a function of strain and strain rate by bulk X-ray Schultz reflection and electron back scattered diffraction (EBSD) revealed development of cube components {001} and {013} with negligible deformation texture components (Cu or brass type) and limited fraction of low angle grain boundaries (< 10 %) in superplastically deformed samples. The reasons for the formation of cube components and their influence on flow behavior of electrodeposited materials were critically analyzed. Additional microstructural investigation by transmission electron microscopy revealed dislocations movement constrained by intragranular particles, leading to strain hardening and cavitation in the nano Ni-P alloy.